If you read it.. it mentions this little thing called TCO (Total cost of Ownership).. which is not JUST the device (laptop or desktop) or Tech Support its:
Hardware (and the replacement cycle) - Macs tend to be replaced less often
Support - Mac's tend to work.. less options/features but for office workers, they use their 2 - 3 applications + email (most of which these days are more web based), not to mention manufacture support. This is a big number depending on the size of the organization.
Software costs - A lot of full functioning software comes with OSX, vs. quite a lot in the windows world are add-ons (ie: cost)
Backend management costs - This is another big cost, but a LOT of package deployment tools, management/monitoring of the hardware, etc... all these things drive up the TCO.
and a lot of others.. all these variables add up.. and depending on the use case makes a strong argument for OSX. It doesn't work in all cases (hey, you are using a windows only app that is core for your business.. not much you can do other than run Windows.. adding VDI/Virtualization drives up cost/complexity).. But again, if you are deploying VDI enmass, then this can impact the numbers as well (ie: less dependency on the user hardware, which means user satisfaction is more important), especially since tightly controlled (by IT) environments running specific applications tend to be viewed more favorably viewed its just "an app" not their work environment.
In short, its a combination of a LOT of variables that is driving the TCO to favour macs.